Means for rectifying alternating currents.



J. L. WOODBRIDGE.

MEANS FOR EEOTIPYING ALTERNATING GURRENTS. APPLIOATION FILED NOV.29, 1909.

1,051,941. y Patented Feb.4,1913.

2 BHEETSSHEET 1.

INVEN T0!) Joscpi Z. mrzie I) I TTUIIIEY.

IV! TNESSES J. L. WOODBRIDGE.

MEANS FOR RECTIFYING ALTERNATING CURRENTS.

APPLICATION FILED NOV. 29, 1909.

1,051,941. Patented-Feb. 4, 1913.

2 sums-sum '2.

49 e 3 f L' I 7 WITNHSES: F 1 6 mmmm M I zfasqollWvdn agre UNITED STATES PATENT OFFICE.

JOSEPH L. WOODBRIDGE, F PHILADELPHIA, PENNSYLVANIA.

mums For. n-Ec'rIrYINe ALTERNATING cuimnn'rs.

tating devices or means for opening the circuit of the alternating current and reversing the connections at or near the instant when 'the current is passing through zero.

Such apparatus is liable to produce troublesome or destructive sparking with sllght variat-ions in the phase relation of thec'urrentr In the apparatus described below the circuit' is at no time'broken' but resistances 7 illustrates one means of providing for the are employed Whose resistance varies with pressure and means are provided for pro-I ducing variation of pressure in synchronism with the current alternations.

Theinvention will be more clearly under stood by referenceto the following description taken in connection .with the accompanying drawings, in which Figure 1, shows one embodiment of the invention applied to a single phase alternating current. circuit. Figs. 2-, 3, and 4,

are diagrams illustrating the combination of forces operating in the apparatus of Fig. 1 under different adjustments. Fig. 5, shows another embodiment of the invention applied to a three phase circuit, and Fig. 6,

Between the two piles is shown a tongue A of magnetic material arranged to vibrate 1n the a r gap D-of amagnetlc circuit M. When this tongue 15 111 its mean position the Specification of Letters Patent.

Application flled November-29, 1909. Serial No. 530,368.

pressure on the. two piles of carbon disks is equal and their resistance is equal and it may be comparatively high so that only a small flow of current will take place through PatentedFeb. 4, 19 13.

them from the alternating. current circuit and a small flow of direct current from the battery in the discharge direction. This latter will divide through the two carbon p1les and passing through the winding of the transformerT from opposite ends will unite again at the middle point returning from there to the battery. If, however, the tongue A is-v'ibrated in synchronism with and in the 'proper phase relation to the alternating ,electro-motive-force on the circuit 1--2 the resistance of the pile K will be reduced at the instant when the alternating current electro-motive-force between the points 3 and 4 is in the proper direction to charge the battery and owing to this reduction in the resistance of the pile K a considerable charging current will flow into the battery during this-half cycle. During the following half cycle the other carbon pile K will be under compression and its resistance reduced, and at'the same time the electro-motive-force between the points 4 and 5 will be in the right directionto charge the battery so that a considerable charging current will flow into the battery during this half cycle also. The battery will therefore receive a uni-directional current under these conditions. A reactance coil is shown at L which will tend to smooth out the pulsations of this current.

In order to produce synchronous vibra tion of the tongue A. and the proper phase adjustment of this vibration the following construction is shown: The tongue is attached to the magnetic frame M by a flexible suspension at F. A steel spring may be used having considerable resilience or an ordinary hinge joint. At the other end of the tongue A is an extension G carryingv anad'justable weight H, which may, slide along the bar G and be clamped at any point by a set screw. Two opposing springs I and I whose tension-may be'adjuste'd by screws J and J are also shown. The relative tension of these s rings will determine just-ing their absolute tension as well as the position of the weight H, the natural period' elastic, permitting t e weight H to overswing to some extent at each end of its travel and prolong the maximum pressure on the carbon piles during each vibration.

In Fig. 2, is shown diagrammatically thevariation of force acting on the tongue A during its vibration. The horizontal line between the points 6-7 represents the travel of the tongue, greatly magnified, while the curved line 8 represents the force acting upon the tongue including the elasticity of the spring F and of the springs I and I and the resisting force of the carbon piles K and K when under compression. While the tongue is traveling from one extreme corresponding to the point 6 to the middle point 9, these forces tend to accelerate its motion, and are therefore represented as positive corresponding with the ordinates of the curve 8 above the line 6-7. Between the point 9 and the point 7 the forces acting on the tongue will oppose its motion and are represented as negative, the curve 8 being below the horizontal line bet-ween these points. These forces will bring the tongue to rest when it reaches the extreme point of its travel and then accelerate it in the 0pposite direct-ion. If these forces were the only ones acting on the tongue itis evident that the vibration would continue indefinitely after once being set in motion. There are. however, other forces such as friction and air resistance as well as the lack of perfect elasticity in the spring and carbon piles, which will oppose the motion of the tongue in each direction. These forces may be represented by the curve 10 when the tongue is moving to the right and by the curve 11 when the tongue is moving to the left. These resisting forces will soon bring the tongue to rest unless counteracted by others which in the aggregate are equal and opposite to them. These latter forces are supplied in the device "shown in Fig. 1 by the magnetic attraction and repulsion produced by the coils C and C wound on the magnetic frame M and by the coil E surrounding the tongue A. Coil E is connected across the terminals of the battery B, and its effect may be controlled by the rheostat R The coils G and C are connected in series across a portionof the transformer T, the number of coils of the transformer T across which, these windings C and C are connected being adjustable 'by means of the multiple point switch S. A rheostat R is also included in this circuit. The coils O and C are 'so wound that when one is producing north polarity at the pole face the other is pro ducing south polarity. Thus when the tongue A is attracted by one pole of the magnet M it will be repelled by the other. These attractions and repulsions will alternate at a frequency corresponding with that of the circuit 12, and will tend to produce vibrations of the tongue A of the same frequency. e v

It remains to show how the apparatus may be adjusted so that the tongue A will vibrate in the proper phase relation to produce the compression on the piles K and 1' at the times when the alternating current electromotive-force is in the right direction to charge the battery, and further that any departure from this phase relation will introduce forces tending to restore it. There are two different adjustments of the apparatus shown in Fig. 1, either of which will accomplish this result. For the first adjustment the resistance in the rheostat R will be entirely out out. The resistance of the coils C and C being comparatively low the counter elect-ro-motive -force developed in its coils will be largely due to the variation of magnetic flux, and since this counter electromotive-force must be equal to that applied to the terminals of the coils, the magnetic flux must, in accordance with the well known law, reach its maximum value in one direction or the other when the potential applied to the coils C and C is passing through zero. The value of this flux will be determined by the potential applied to the terminals C and C as adjusted by the switch S, and the force exerted on the tongue A by this flux may be adjusted by varying the curve 13 corresponding with motion in the opposite direction. It will be seen that these curves more than counter-balance the curves Y10 and 11 representing the retardingforces of friction, etc. Under these conditions the vibration of the tongue A would tend to increase, first in amplitude, and therefore in frequency since the'force represented by the line 8 increases rapidly at each extreme of the travel with anyincrease in the amplitude. This momentary increase in frequency of vibration will change the phase relations shown in Fig.2, so that the magnetic force represented by the dotted lines 12 and 13 will become retarded with reference to the other forces. This new condition is illustrated in Fig. 3, the full lines remaining the same as in Fig. 2, while the dotted lines reach their maximum values a little later.

It will be seen that the aggregate effect of 1 mates,

the magnetic force represented by the dotted lines in Fig. 3 is less than it was in Fig. ,2, tlns aggregate being represented by the shaded area which is less than the area in-' tween the curve and the horizontal line 6 -7 no further phase displacement will take place and thet'ongue will continue to vibrate in this phase relation. A careful ustment of the switch' S and the rheost-a-t R will produce this condition of stability with only a very slight phase displacement, and the tongue A will be in its mean position when the magnetic flux in the magnet M is substantially at its maximum, and therefore when the electro-motive-force across the circuit 1--2 is at or near zero. This adjustment will therefore produce the desired rectification of the alternating current.

The second adjustment will be'producedby including a very considerable resistance in series with the coils C and C by means of the rheostat 13 Under thesecondit-ions the largerpart of the counter electro-motiveforce in the circuit containing the coils G and C will be that due "to the ohmic drop in the rheostat R The current in this'circuit will then be substantially in phase with the applied elect-ro-motive-force producing a magnetic flux in the magnet M and across the air gap D. which will reach its maximum value at the instant of maximum potential across the circuit 12. The magnetic forces of attraction and repulsion produced by this adjustment will then be as shown in Fig. 4. In this figure the full lines are the same as in Figs. 2 and 3. and have the same significance. The dotted lines 12 and 13 represent as before the forces due to the magnetic flux,

but since this flux is now nearly in phase withthe electro-motive-force the adjustment must be such that the lines 12 and 13 will pass through zero when the tongue A is near-its meanposition and the adjustment must be such that the line 13 will cross the horizontal line 6-7 a little to the left of the middle point 9 but as near thereto as possible. while the line 12 crosses a little to the right of this point. The shaded area between these two lines willthen represent the aggregate forcetending to counterbalance the friction, air resistance,'etc. It will be seen that if the frequency of vibration of the tongue A tendsto slow down slightly, gi-' ing an increased lead to the alternating current electro-motive-force and the corresponding magnetic flux, the line 13 will cross. the line 6-7 a little earlier, that is. nearer to h po nt 6, and th l 12 wi r s h lin -7 a li le a l on the re urn tra l, that is, a little nearer to the point 7, which will increase the area included between the lines 12 and 13 thus .increasing the force tending tomaintain the proper "frequency and phase relation.

The lines 12 and 13 in Fig. 4 which representthe variation of magnetic flux will also represent, the magnetizing current in the coils C and C which produces this flux, and as this current will be. displaced somewhat inthe lagging direction from the applied elect-ro motive-force, this applied electromotive-force will pass through its zero value a little earlier than the current and fltlX, for example atthe points .17 and 18 in the travel of the tongue as shown in Fig. 4, It is desirable to have these points of zero electro- Inotive-force'as near as possible to the middle point- 9, but in order to accomplish this it will be seen that the current and magnetic flux would have to be leading instead of lagging. To produce this result a condenser (l is shown on Fig. .1 in series with the coils Q and G which wmild be shortcircuited by the switch P .for the first adjustment described above, but can be open circuited by opening the switch P fpr the second adjustment. The capacity of this condenser may be chosen to give a leading phase position to the current and the mag netic flux so as to bring the points 17 and 18 to coincide With the point 9 or nearly so.

The second adjustment has certain advantages over the first. It will be noted from Fig. 4- that the force exerted by the. magnet on the tongue A reaches its maxi-' mum near the extreme limits of the travel thus assisting to increase the pressure on the carbon piles, whereas in the first adjustment this force is passing through zero at its ex treme limits. Furthermore, since the area included between the curves 12 and 13 is fixed by the retardin forces of friction, air resistances, etc, whic must be counteracted, these two curves will approach nearer to each other the greater their maximum height. \Vhen the magnetizing force is comparatively small these curvesmust be farther apart which 'will throw the vibration of the tongue A somewhat out of phase with the electro-motive-force, and thus reduce the charging current into the battery. As the magnetizing force, is increased the curves 12 and 13 will come closer together bringing the vibration of the tongue A more closely into phase. with the electro motive-force and increasing the charging current. The increase in the magnetizing force will also increase the maximum pres sure on the carbon piles and still further increase the charging current. With this-atljustment therefore. the amount. of charging current can be readily varied over a wide range by manipulating the rheostats It and R? or the switch S. With the first adjustment, however, this cannot be so readily accomplished. Thecurves 12 and 13 in Fig. 2 must have a slightly greater maximum than the curves 10 and 11, in order to insure stability with any slight changes in the opposing forces of friction, air resistances, etc. Any increase in the magnetizing force will throw the vibration of the tongue A farther out of phase, while having only a slight effect on the maximum pressure on the carbon'piles.

In Fig. 5 a three phase alternating current circuit 2122-23 is shown, to which is connected a three phase auto-transformer T .Three piles of carbon disks K K and K are shown, one terminal of each being connected to the corresponding terminal of the transformer T The other three terminals of the carbon piles are connected to a common junction point 30 and a storage battery B is connected between the common junction point 27 of the transformer T and the junction point 30. The three carbon piles are intermittently compressed in sequence by the three rods P, P and P respectively. These rods are given a reciprocating mot-ion by means of the pin 31, which is mounted eccentrically upon and rotated by the'shaft 32. This shaft is driven by the synchronous motor M connectedto the circuit 2l-22-23 its field 33 being excited from the battery. It will be seen that each of the carbon piles is connected in series between one phase of the three phase .circuit and the battery. The adjustment of the apparatus is such that the maximum compression on each carbon pile is produced when the potential between the corresponding conductor of the three phase circuit and the neutral point 27 is a maximum in the direction to charge the battery. This permits-the maximum current to flow into the battery in the charging direction through each carbon pile in succession, the pressure on each being released when the polarity reverses to prevent any appreciable flow of current in the opposite direction.

The phase relation between the electro motive-force on the circuit 21-2223 and the rotation of the pin 31 may be adjusted in many well known ways. Fig. 6 illustrates one of these methods. The shaft 32 shown in Fig. 5 is divided in Fig. 6 into two parts '4142, which abut and are sur rounded by a sleeve 43. Mounted on the two parts of the shaft are pins 46 and 48,

which engage in slots 47 and 49 in the sleeve. Slot 47 is parallel with the axis of the shaft while the slot 49 is inclined thereto, so that by sliding the sleeve in one direction or the other, the angular relation of the two-parts of the shaft may be adjusted. The position of the sleeve may be shifted by means of the collar 44 and the fork 45.

It will be obvious that many modifications may be made in the details of the invention without departing from the spirit thereof.

What I claim as new and desire to secure by Letters Patent is- -1, In adevice for rectifying alternating currents, a body of material whose electrical resistance varies with pressure and having both alternating and direct current connections, and means for applying to said body pressures varying in synchronism with the alternations of electro-motive force.

2.-In combination an alternating current circuit, a direct current circuit, a body of material whose electrical resistance varies with pressure connected between said circuits and means for applying to said body pressures varying in synchronism with the alternations of electro-motive-force in the alternating current circuit.

. 3. In combination an alternating current circuit having a plurality of conductors, a direct current circuit, a body ofmaterial whose electrical resistance varies, with pressure connected between each conductor of the alternating current circuit and the direct said bodies pressures varying in sychronism with the alternations of electro-motive-force on the alternating current circuit.

' 4. In combination an alternating current circuit having a plurality of conductors, a direct current circuit, a body of material whose electrical resistance varies with pressure connected between each conductor of the alternating current circuit, and one side of the direct current circuit, and means for applying to each of said bodies pressures varying in synchronism with the alternations of electro-mot-ive-force on the alternating current circuit.

5. In combination, an alternating current circuit, a direct current circuit, a body of material whose electrical resistance varies with pressure connected between said circuits, means for'applying to said body pressures varying in synchronism with the alternations of electro-mo-tive-force on the alternating current circuit, and means for adjust ing the phase relation between'said pressures and the alternations of electro-motive-force.

6. In combination an alternating current circuit, a direct current circuit, a body of material whose electrical resistance varies with pressure'connected between them, an electro-magnet, a magnetic member arranged in the magnetic field of said electromagnet and adapted to apply varying pressures to said body, and means for applying to the electro-magnet an alternating excita tion in synchronism with the alternating 1 current electro-motive-force.

7. In combination, an alternating current circuit, a direct current c1rcu1t,'a closed conducting circuit of variable rmistance connecting the two, and means or varying the resistance of the conducting c rcuit 111 synchronism with the alternations of electro- -C1ICl11l2, a direct current circuit, a body of motive'force on the alternating current circuit without opening said conducting circuit.

8. In combination, an alternating current circuit, a direct current circuit, a body of material whose electrical resistance varies with pressure connected between 'said circuits and electromagneticmeans including windings connected respectively to the alter- 'nating current, and to the direct current circuit for applying to said body pressures varying in synchronism with the alternations of electro-motive-force on the alternating current circuit 7 v 9. In combination an alternating current circuit, a direct current circuit, a body of .material whose electrical resistance varies with pressure connected between them, electro-magnetic means including windings connected respectively to the alternatingcurrent and the direct current circuits for applying synchronously varying pressures to said body, and means for adjusting the phase relation between the variations of pressure and the alternating electro-motiveforce of the alternating current circuit.

10. In combination an alternating current circuit, a direct current circuit, a body of material whose electrical resistance varies with pressure connected between them, an electro-magnet, a magnetic member arranged in the magnetic field of said electromagnet and adapted to apply varying pressures to said body, means for applying direct current excitation to said member, means for applying alternating current excitation to the electro-magnet, and means for adjusting the phase relation ofsaid alternating current excitation;

11. In combination an alternating current circuit, a direct current circuit, a body of material whose electrical resistance varies with pressure connected between them,

an electrormagnetic deviceincluding a stationary member and a movable member whereof the latter is ada ted to apply varying presures to said bo an exciting coil for each of said members, means for trans-s mitting direct current through one of said coils, meansv for transmitting alternating current throughthe other coil, and means foradjusting the phase relation of said alternating current. 12.-In combination an alternating current circuit, a direct current circuit, a body of material whose electrical resistance varies withipressure connected between them, an

the latter is adapted to applyvarying prescss'ures to said body,an exciting coil on one of said members connected to the alternating current circuit, and an electrical condenser connected in series'with the coil. 7

13. In combination an alternating current material whose electrical resistance varies with=pressure connected between them, a vibrating piece adapted to apply varying pressures to said body, means for ad ust1ng the natural period of vibration of said vi.- brating piece, and means for applying to said piece magnetic forces to maintain its vibration-in synchronism with the electromotive-force of the alternating current cir' cuit.

'14. In combination an alternating current circuit comprising two conductors, means for maintaining a neutral point .ofinterme; diate potential with respect to said circuit, a storage battery,connection from one terminal of said battery to said neutral'point,

'circuit comprising two conductors, means for maintaining a neutral point of intermediate potential with respect to said circuit, a storage battery, connect-ion from one terminal of said battery to said neutral point, two circuit connections from the other battery terminal, one to each of the two con-- ductors of. the alternating current circuit,

two bodies of material whose electrical resistance varies with pressure, one connected into each of the two circuit connections last named, a vibrating piece arranged to apply pressure alternately to the two bodies, an

electro-magnetic device for maintaining the vibration of said piece, a coil vconnected to the alternating current circuit for exciting said device, and a condenser in series with saidcoil. I

16. In combination an alternating current circuit," a direct current circuit, a body of material Whose electrical resistance varies with pressure connected between said circuits, an electro-magnetic device for apply ing varying pressures to said body, an exciting coil for said device, and means for transmitting through said coil alternating currents in synchronism with the electromothe force on the alternating current circuit and substantially in phase therewith.

17. In combination an alternating current circuit, a direct current circuit, a body of 1 mgterial whose electrical resistance varies 1 In testimony whereof I have hereunto mth pressure mnnected between said cir signed my name.

cuits an electra-magnetic device for apply mg aryilng pmpm a? said body may JOSEPH L. WOODBRIDGE. cltmg 0011 for send device, and means'for wltneesesi varying the current strength in said coil to FRANK E. FRENCH,

control the maximum pressure on said body. K. M. GILLIGAN. 

